Discussion
To this day, data on PH and IH is often pooled, even though several studies suggest that these hernias are different entities [
6‐
9]. The present analysis of 9159 patients of the prospective French Hernia Club database validates previous research stating that PH and IH are significantly different in terms of most baseline, surgical and hernia characteristics, and postoperative outcomes. After correcting for hernia width, however, most outcomes no longer showed significant differences, indicating that not the type of hernia, but the hernia width is an important factor that largely contributes to these differences.
IH repair is often considered as a procedure with an increased risk of intra-operative and postoperative complications compared to PH repair. Based on the data in the present study this assumption seems only partly correct. The emphasis should be on hernia size instead of hernia type. In accordance with previous studies by Heniford et al
. [
17] and Helgstrand et al. [
18], the present study shows that with increasing hernia size, the complication rate increases, as well as the re-intervention rate. Both intra-operative-, wound- and surgical complication rates, as well as the re-intervention rate, are not statistically significantly different when comparing PH and IH per width category. The width distribution is skewed, with a larger average width for IH compared to PH, indicating that not the type of hernia, but the hernia width is an important factor causing the differences between IH and PH found in this study and the previous study by Kroese et al
. [
7]. Repair of small IHs should be viewed as low-risk procedures, as the complication rates are similar to the rates of small PHs. In relation to this, large PHs should not be underestimated, as these have as many intra-operative, wound- and surgical complications as large IHs. However, this is not the case for medical complications, which are more common in patients with IH with a width of 3–4 and 5–10 cm. Patients with IH in these width categories are significantly older and have a higher incidence of a history of chemo- or immunotherapy and a higher incidence of anti-coagulant use compared to patients with PH. This indicates a higher incidence of cancer patients and/or patients with vascular disease and possibly a worse overall condition, making them more susceptible to medical complications. As a possible result of this, the admission duration was significantly longer for patients with IH compared to patients with PH, regardless of any width category.
Although worse outcomes of IH mostly appear to be the result of larger width, hernia type and hernia width cannot be viewed separately from each other. PH and IH have different etiologies. PH seems to be a congenital condition or the result of a prolonged period of increased intra-abdominal pressure, IH being the result of failed wound healing of often large incisions, possibly explaining why IH is in general larger compared to PH. There is extensive evidence that in IH changes in the homeostasis of the extracellular matrix (ECM), especially switches in collagen phenotypes, are prominent [
19]. It is likely that there are similar changes in the ECM of PH. However, to our knowledge, there is no study examining ECM changes in which data on IH and PH is not pooled. Future research examining whether differences between the ECM of PH and IH explains differences in hernia size and outcomes is necessary.
A meta-analysis by Stabilini et al
. [
9] found that IH has a higher recurrence rate than PH. However, the question remains whether this is still the case after correcting for hernia width. Hernia recurrence is not reported in the present study due to insufficient data on PH recurrence in the Hernia Club database. A probable explanation for this is the fact that PH has a smaller average width, less frequently having concomitant defects at the surgery and a shorter operative time, resulting in a simpler procedure and, subsequently, a shorter post-operative follow-up period compared to patients with IH, resulting in less available data on PH recurrence [
9]. As both the formation of IH and hernia recurrence are the result of failed wound healing, it seems logical that hernia recurrence is more common in IH. Nevertheless, several studies have shown that larger hernias have a higher recurrence rate compared to smaller hernias, forming another possible explanation of the higher recurrence rates of IH of around 30% [
18,
20‐
22].
Limitations
This study is limited by the fact that the data are not randomized, which may cause a potential risk of confounding by indication. However, since all patients who underwent ventral hernia repair were included in the registry, no selection has been made in patient inclusion and this study is, therefore, a good representation of the general patient population. Still, in the present study, 46% of the patients had IH which is much higher than the expected 30% found in previous research, and could potentially indicate a risk of selection bias [
23]. A possible explanation for this higher percentage is the fact that de Hernia Club registry is the collaborative work of surgeons with a special interest in hernia surgery, and might, therefore, attract more complicated patients. The expertise of the surgeons might also explain the relatively low rate of complications.
The incidence of PH with a width of > 10 cm is low (n = 16). Therefore, statistically reliable conclusions on hernias wider > 10 cm cannot be made, since this study is underpowered for this width category. However, the other width categories showed an increase in complication and re-intervention rates with increasing width. It is, therefore, likely that this can be extrapolated for hernias with a width of > 10 cm.
Hernia width is missing in 20.1% of PH, whereas this is only 3.1% in IH. As a result, only 80% of data on PH was available for the analysis per width category. This might be because ultrasounds or CT scans are less often performed for the clinical workup before PH repair. This may be more commonly performed for IH, since this hernia type is often larger, more complex, and sometimes has multiple fascial defects.
Acknowledgements
We would like to thank all the members of the Hernia-Club for collecting patient data.
The names of the members of the Hernia-Club: Abet E (Centre Hospitalier, La Roche sur Yon, France), Ain J-F (Polyclinique de Val de Saône, Macon, France), Arnalsteen L (Hôpital Privé La Louvière, Lille, France), Baraket O (CHU, Bizerte, Tunisia), Beck M (Clinique Ambroise Paré, Thionville, France), Bellouard A (Clinique l'Archette, Olivet, France), Benizri E (CHU, Nice, France), Berney C (Bankstown-Lidcombe Hospital, Sydney, Australia), Bilem D (Sidi-Bel-Abbes, Algeria), Binot D (MCO Côte d’Opale, Boulogne sur Mer, France), Blanc B (CH, Dax, France), Blazquez D (Clinique Jeanne d’Arc, Paris, France), Bonan A (Hôpital Privé d’Antony, Antony, France), Boukortt T (Cliniq, ue, Chlef, France), Brehant O (Abbeville, France), Cas O (Centre Médico Chirurgical–Fondation WALLERSTEIN, Arès, France), Champault-Fezais A (Groupe Hospitalier Paris St Joseph, Paris, France), Chau A (CHU, Lille France), Chollet J-M (Hôpital Privé d’Antony, Antony, France), Constantin M (CH, Troyes, France), Cossa J-P (CMC Bizet, Paris, France), Dabrowski A (Clinique de Saint Omer, Saint Omer, France), David A (CHU, Bordeaux, France), Demaret S (Clinique, Besançon, France), Dubuisson V (CHU, Bordeaux, France), Dugue T (Clinique de Saint Omer, Saint Omer, France), El Nakadi I (CHU, Bruxelles, Belgium), Faure J-P (CHRU Poitiers, Poitiers, France), Frileux P (Hôpital Foch, Paris, France), Fromont G (Clinique de Bois Bernard, Bois Bernard, France), Gadiri N (CHU, Tlemcen, Algeria), Gillion J-F (Hôpital Privé d’Antony, Antony, France), Glehen O (CHU, Lyon Sud, France), Hennequin S (CH, Cahors, France), Isambert M (Clinique Capio, La Rochelle, France), Jurczak F (Clinique Mutualiste, Saint Nazaire, France), Khalil H (CHRU Rouen, Rouen, France), Lamblin A (Clinique, Lille, France), Largenton C (Saint Lô, France), Lavy M (CH Saint Joseph, Lyon, France), Lepère M (Clinique Saint Charles, La Roche-sur-Yon, France), Le Toux N (Clinique Jeanne d’Arc, Paris, France), Magne E (Clinique Tivoli, Bordeaux, France), Manfredelli S (CHU, Strasbourg, France), Mariette C (CHU, Lille, France), Marion Y (CHU, Caen, France), Mercoli H-A(CHU, Strasbourg, France), Mesli Smain N (CHU, Tlemcen, Algeria), Moszkowicz D (CHU, Boulogne, France), Najim M (Clinique Yasmine, Casablanca, Morocco), Oberlin O (Croix St Simon Diaconesses, Paris, France), Odet E (CH, Macon, France), Ortega Deballon P (CHU, Dijon, France), Pavis d’Escurac X (Strasbourg, France), Pichot Delahaye V (Polyclinique de Rillieux, Lyon Nord, France), Putinier JB (CH mutualiste, Grenoble, France), Regimbeau JM (CHU, Amiens, France), Renard Y (CHRU Reims, Reims, France), Romain B (CHV, Lausanne, France), Rouquie D (Clinique Pasteur, Royan, France), Soler M (Polyclinique Saint Jean, Cagnes-sur-Mer, France), Soufron J (Clinique Notre Dame, Vire, France), Roos S (Clinique Claude Bernard, Albi, France), Thillois J-M (Hôpital Privé d’Antony, Antony, France), Tiry P (Clinique de Saint Omer, Saint Omer, France), Vauchaussade De Chaumont A (CHU Broussais, Paris, France), Vinatier E (CH, Seclin, France), Vu P (HPMV, Bry sur Marne, France), Verhaeghe R (MCO Côte d’Opale, Boulogne sur Mer, France), Zaranis C (Clinique de La Rochelle, France), and Zeineb M (AHU, La Marsa, Tunisia).